Injection drug users are at increased risk for progressing from tuberculous infection to active tuberculosis. Preventive therapy with isoniazid is highly effective in reducing the incidence of tuberculosis in tuberculin skin test positive persons, but completion of at least six months therapy is necessary. Adherence to isoniazid preventive therapy is often extremely poor, particularly among injection drug users. We propose to evaluate three interventions to enhance adherence to preventive therapy in tuberculin skin test positive injection drug users who are candidates for isoniazid. Subjects will be recruited from the Baltimore City Health Department Chest Clinic and will be randomized with a factoral design to a 3 X 2 intervention assignment. One third of subjects will be assigned to self- administered therapy with monthly support group meetings and education by a peer educator; one third will be assigned to twice weekly supervised therapy by a licensed nurse; and one third will serve as controls, receiving usual clinic-based, self-administered therapy with standard education. Additionally, subjects in each of the three primary groups will be randomized to receive either immediate or deferred monetary incentives for completing therapy. Patients assigned to immediate reimbursement will be paid $10 each month that they are compliant with medication and keep their monthly appointment. For patients assigned to deferred compensation, an escrow account will be established and $10 will be deposited for each of six months of completed therapy. When six months are completed the subject will receive the entire reimbursement of $60. All subjects will be interviewed at enrollment and at six months to determine knowledge, attitudes and health beliefs pertinent to tuberculosis preventive therapy. We will enroll 100 subjects into each of the primary intervention groups, for total of 300 subjects. 150 will be randomly assigned to receive each of the financial incentives to complete therapy. We will have 88% power to detect a 15% increase in compliance with therapy according to financial incentive and a 18% increase in compliance comparing subjects receiving enhanced intervention or directly observed therapy with controls. This project will contribute to treatment guidelines and public policy for the control of tuberculosis in injection drug users.